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Abstract

This paper reports the final results of research into weedy Sporobolous spp. grass control using fertiliser in coastal central Queensland. In 2014/2015 a single application of herbicide pellets, GP Flupropanate® (e.g. 86.9 g/kg flurpropanate, produced by Granular Products) was applied (label rate, 13kg/ha) across 4 ha at two sites located at Miriam Vale and Byfield. The Miriam Vale site was heavily infested (60%) with giant rat’s tail grass (GRT) (Sprobolous pyramidalis), whereas at the Byfield Site contained 50% Parramatta grass (S. africanus). Half of each site also received an application of Nitrogen (N) and Phosphorous (P) fertiliser, after the herbicide was applied. A second application of fertiliser was applied a year later, and the Byfield Site received a third application of fertiliser in October 2017. The results of the Miriam Vale site were reported in 2015 (Reeve et al 2015) and this paper will focus on the results from the Byfield site.After the first fertiliser application, the pasture legume round-leaf cassia cv. Wynn (Chamaecrista rotundifolia) grew vigorously creating a mixed sward that also included humidicola (Brachiaria humidicola) and Parramatta grass. During winter, when this legume is most palatable, the mixed sward was readily consumed by cattle. After fertiliser was applied in the second year, 93% of the pasture dry matter was the improved and highly competitive tropical sown grass humidicola, compared to 40% in unfertilised area. At the same time, Parramatta grass accounted for 2.8% of the fertilised pasture, compared to 6.5% in the unfertilised and 50% in the unstocked and unfertilised area. After the initial application of herbicide, there has been very successful, herbicide free, control of the Sporobolous spp using commonly available fertiliser at economical rates that also resulted in increased pasture productivity and quality.